cost energy ash in place stabilized
TRANSCRIPT
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 1/15
Road Materials and Pavement Design, 2013
Vol. 14, No. 3, 537–550, http://dx.doi.org/10.1080/14680629.2013.779302
Cost, energy, and greenhouse gas analysis of fly ash stabilised cold in-placerecycled asphalt pavement
Xiaojun Lia, Haifang Wena*, Tuncer B. Edilb, Renjuan Sunc and Timothy M. VanRekena
a Department of Civil & Environmental Engineering, Washington State University, 405 Spokane Street,
Pullman, WA 99164, USA; b Department of Civil & Environmental Engineering, University of Wisconsin- Madison, 1415 Engineering Drive, Madison, WI 53706, USA; cSchool of Civil Engineering, Shandong University, 17922 Jingshi Road, Jinan 250061, People’s Republic of China
The purpose of this study is to evaluate the performance, costs, energy, and greenhouse gasemission of cementitious high-carbon fly ash (CHCFA)-stabilised recycled pavement materials(RPMs) as base course. Three test road cells were built in Minnesota. These cells have the same
pavement structure except different base courses: conventional crushed aggregates, untreated RPM, and CHCFA-stabilised RPM. Results of laboratory and field tests were used in the
Mechanistic-empirical pavement design guide (MEPDG) to predict the pavement performance.MEPDG performance prediction indicated that Cell 79 containing CHCFA-stabilised RPM had the longest service life in the three cells. The life-cycle analysis indicated that the usage of the CHCFA-stabilised RPM as the base of the flexible pavement can significantly reduce thelife-cycle cost, energy consumption, and greenhouse gas emission.
Keywords: performance; cost; energy; greenhouse; stabilisation; base
1. Introduction
Due to the increasingly stringent environmental policy stipulated by the Environmental Protection
Agency and/or local authority, the power-generation industry must take measures to reduce the
emission of nitrogen oxides (NOx), sulphur oxides (SOx), and mercury (Hg). Low-NOx burners
reduce emissions by changing the combustion characteristic of coal boilers, but they increase
the amount of residual unburned carbon in fly ash. Additionally, activated carbon is injected to
reduce Hg emission, which also increases the carbon level in fly ash. Increased carbon levels
in fly ash make air-entrained concrete production more difficult (Ramme & Tharaniyil, 2000).
High-carbon fly ash can reduce the durability and workability of concrete significantly (Bhatty,
Gajda, & Miller, 2003). Even though some measures exist to beneficiate high-carbon fly ash, such
as carbon/ash separation and reburning ash as a fuel for coal boilers, there are disadvantages to
these technologies. The carbon/ash separation process consumes energy and ash reburning needs
a burner capable of producing marketable fly ash. Therefore, direct utilisation of cementitious
high-carbon fly ash (CHCFA) without treatment is still the best possible scenario to consume
high-carbon fly ash.
Simultaneously, quarrying virgin aggregate for highway construction also results in environ-
mental problems and energy consumption. An alternative to quarrying virgin materials is in-place
recycling of asphalt pavement. This recycling process is relatively inexpensive and contributes
towards sustainable pavement rehabilitation (Koch & Ksaibati, 2010). Existing hot-mix asphalt
*Corresponding author. Email: [email protected]
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 2/15
538 X. Li et al.
(HMA) layer is pulverised and blended with some of or the entire base course to form a broadly
graded material referred to as recycled pavement material (RPM) (Li, Benson, Edil, Hatipoglu,
& Tastan, 2008). There is an increasing trend towards recycling existing asphalt pavement and
using as base course for the new pavement (Sullivan, 1996). However, there are concerns on the
load-carrying capacity and deformability of a base layer made of RPM (Koch & Ksaibati, 2010;
Senior, Szoke, & Rogers, 1994). Mechanical or chemical stabilisation of RPM are often needed to improve the engineering properties. There is a potential to use CHCFA as the admixture to
stabilise the RPM in pavement recycling.
It will have great environmental and cost benefits if CHCFA can be used to stabilise RPM in
pavement construction. However, before CHCFA-stabilised RPM base layer can be promoted
in the industry with confidence, a comprehensive knowledge about its material properties and
performance, a quantification of its life-cycle cost and environmental benefits, such as the energy
consumption and greenhouse gas emissions, is imperative. In order to comparatively evaluate the
performance and effectiveness of CHCFA-stabilised RPM base course material in a real highway
construction, three test cells at MnROAD test facility were built, with the same asphalt surface
layer, subbase, and subgrade, but three different base courses: conventional crushed aggregates,untreated RPM, and CHCFA-stabilised RPM materials.
2. Construction
In this study, three flexible pavement test cells with different base materials were constructed at the
MnROAD test facility to evaluate the effectiveness of RPM with and without fly ash addition and
to compare them with traditional crushed aggregate base course which is a Minnesota Department
of Transportation (MnDOT) Class 6 granite aggregate (Clyne & Palek, 2008). The MnROAD test
facility is a two-lane pavement test track located about 64 km (40 miles) northwest of Minneapolis.
A 12.7 cm (5 in.)-thick clay subbase was placed and compacted over existing subgrade soils inCells 77, 78, and 79. The RPM base course, Class 6 aggregate base course, and CHCFA-stabilised
RPM base course were installed in Cell 77, Cell 78, and Cell 79, respectively. For the CHCFA-
stabilised RPM base course, the contractor added 14% of fly ash based on the dry weight of the
RPM. Two lifts of 5.08 cm (2 in.) of bituminous concrete-wearing course were placed about a
month after the placement of subgrade and base course materials in Cells 77, 78, and 79. When the
placement of the wearing course was initiated in Cells 77 and 78, the base material appeared to be
unstable under the weight of the paving machine and other construction traffic. It was discovered
that the subgrade material in Cells 77 and 78 had become very wet possibly due to the excess
precipitation following the placement of the base course materials. The subgrade material in Cell
79 was protected from excessive seepage of rain water, probably due to the presence of the flyash-stabilised RPM. Therefore, the base course material from Cells 77 and 78 was removed.
The subgrade clay material was disked to dry it out and then compacted to the required density.
Following the compaction of subgrade material, the RPM and Class 6 aggregate base courses
were placed again in Cell 77 and Cell 78, respectively. Cell 79 was completed in September 2007
and Cells 77 and 78 were completed in October 2007.
3. Laboratory tests and results
Observing the field performance of the pavement and materials will require many years of service.
Therefore, the performance of pavements was predicted by the Mechanistic-empirical pavement design guide (MEPDG) in which various laboratory testing results were needed. The test samples
were taken in the construction field
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 3/15
Road Materials and Pavement Design 539
3.1. Asphalt concrete material
3.1.1. Binder
The Elvaloy/PPA binder used in this research meets PG 64-34 requirements. The dynamic shear
reometer (DSR) test results of the binder after rolling thin film oven aging are shown in Table 1
and input to the MEPDG programme.
3.1.2. Hot mixed asphalt
Two different sets of loose HMA mixtures, Cells 77, 78, and 79, were sampled at the MnROAD
facility. The sampled HMA was used for the dynamic modulus and the creep compliance tests.
3.1.2.1 Dynamic modulus of HMA. Dynamic modulus is needed in the MEPDG for the pave-
ment analysis and determination of stress/strain which will be used in the performance modelling.
The dynamic modulus was tested at temperatures of −10◦
C, 4◦
C, and 21◦
C. The dynamic modu-lus at temperature of 54.4◦C was predicted based on the time-temperature superposition principle,
as shown in Figure 1. These results were input to the MEPDG programme.
3.1.2.2 Creep compliance of HMA. The creep compliance was tested at −36◦C, −24◦C, and
−12◦C and was shifted to the MEPDG-required temperature of −20◦C, −10◦C, and 0◦C based
on the time-temperature superposition principle, as shown in Figure 2. The creep compliance was
input to the MEPDG to characterise the thermal cracking.
Table 1. DSR test results of the Elvaloy/PPA binder.
Temperature (◦C) G∗/Sin δ (Pa) Phase angle (δ) G∗ (Pa)
64 3900 69.0 3640.96258 7700 66.2 7045.18652 15,000 63.7 13447.29
Figure 1 The measured and predicted dynamic moduli used in MEPDG modelling
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 4/15
540 X. Li et al.
Figure 2. The measured and predicted creep compliance used in MEPDG modelling.
3.2. Base course materials
During construction, the base course materials were sampled and stored for laboratory testing.
The CHCFA-stabilised RPM specimens were fabricated in the laboratory. The moisture-density
relationship of RPM, CHCFA-stabilised RPM, and Class 6 were obtained in accordance with
ASTM D 1557. Resilient modulus ( M r) was determined in accordance with the National Coop-
erative Highway Research Programme 1-28A test protocol (Witczak, 1997). The field density
and moisture contents of base materials on site were measured using a nuclear density gauge.
The field densities and moisture contents were used to fabricate laboratory specimens for
testing.
3.2.1. Fly ash
Fly ash obtained from Unit 8 of the Riverside Power Plant in Minneapolis, MN (operated by Xcel
Energy) was used to stabilise the RPM. This fly ash has a calcium oxide (CaO) content of 22.37%
and a carbon content of 16.35% which is a CHCFA. A fly ash application rate of 14% by weight
of dry mix was used to stabilise RPM as base course.
Figure 3 The gradation of RPM and Class 6 aggregate
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 5/15
Road Materials and Pavement Design 541
Table 2. Parameters in the resilient modulus model.
Base type k 1 k 2 k 3 k 6 k 7
Clay 2380.4971 0.8451 −5.4203 −9.4677 1.0317Class 6 376.4932 1.4858 −0.7325 −67.4420 1.0000
RPM 764.7781 1.2642 −1.0341 −55.4167 1.0000RPM + CHCFA 7D 31,194.3790 0.1545 −0.4353 −8.9163 1.0301RPM + CHCFA 28D 50,966.4110 0.1424 −0.6308 0.0000 1.0000
Figure 4. Resilient modulus test results of field-sampled materials.
3.2.2. RPM and Class 6 aggregate
3.2.2.1 Gradation. The RPM was produced by pulverising the in-situ asphalt pavement at
MnROAD. The RPM consisted of 50% of recycled asphalt pavement and 50% of existing crushed
aggregate base course. The Class 6 aggregate is a granite base course material used by MnDOT.
The gradations of the RPM and Class 6 are shown in Figure 3.
3.2.2.2 Resilient modulus. The resilient modulus model in the MEPDG is shown by Equation
(1) (Witczak, 2004). The parameters for different base materials were resolved by fitting the test
data with the model and are shown in Table 2. The resilient moduli reported in Figure 4 was
predicted by the resolved model at the peak cyclic stress of 103 kPa and confining stress of 45 kPafor aggregate base, and peak cyclic stress of 41 kPa and confining stress of 14 kPa for subgrade
(Witczak, 2004). Figure 4 indicates that the CHCFA-stabilised RPM has a much higher resilient
modulus at 28 days curing age than that at 7 days of curing age, and has much higher resilient
modulus than untreated RPM and Class 6 aggregate.
M r = k 1 ∗ P a
σ b − 3k 6
P a
k 2
∗
ιoct
P a+ k 7
k 3
, (1)
where M r = resilient modulus, psi; k 1, k 2, k 3, k 6, and k 7 = regression constants (obtained by
fitting resilient modulus test data to the equation); σ b = bulk stress = σ 1 + σ 2 + σ 3; σ 1, σ 2, and σ 3 = the major, intermediate, and minor principal stress, respectively; P a = normalising stress
(atmospheric pressure); τ = octahedral shear stress
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 6/15
542 X. Li et al.
Figure 5. The average FWD back-calculated base moduli by ‘MODULUS’.
4. Field tests and results
Falling weight deflectometer (FWD) tests were conducted directly on the base courses during the
construction. Prior to the placement of HMA, the base course had one month of curing. After the
placement of HMA surface, FWD tests were conducted on HMA to back-calculate the modulus
of base materials.
FWD tests were conducted using a 40 kN (9000 lbf) load level which represents the load level
exerted by a dual-wheel load. The modulus back-calculation of the FWD test on the base coursewas based on the equations developed by George, Bajracharya, and Stubstad (2004). For the
modulus back-calculation of the FWD test on HMA surface, the Texas Transportation Institute
(2001) software MODULUS was used.
Figure 5 summarises the averaged back-calculated moduli at different testing dates.
The CHCFA-stabilised RPM had higher moduli than unstabilised RPM, followed by Class 6.
The back-calculated moduli of the base courses from FWD tests were extremely high in the Win-
ter season when the base course materials were frozen (as indicated by the temperature gauges
placed in the base course). The moduli of base courses were lower in Spring than the moduli
in other seasons, indicating the weakening of materials by the Spring thaw. The back-calculated
moduli of base materials from the FWD tests on HMA surface were higher than those tested
directly on the base course during construction. One unexpected result is that the back-calculated
moduli of the CHCFA-stabilised RPM did not show significant increase with the increase of cur-
ing age. This might be due to the micro-shrinkage crack within the CHCFA-stabilised RPM layer
which compensated for the strength increase. However, this assumption needs further study. It
should be noted that although the back-calculated moduli of CHCFA-stabilised RPM are higher
than the other two base materials, the difference is not as significant as the difference between the
laboratory-tested resilient moduli, as shown in Figure 4.
5. MEPDG performance prediction and results No distresses have been found three years after the construction. The observation of the field
performance of pavement and materials may need many years of service Therefore the service
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 7/15
Road Materials and Pavement Design 543
Figure 6. Truck configuration (MnDOT).
Table 3. The traffic configuration (MnDOT).
The traffic configuration Weight ( N )
Total weight 353,634Steering axle 53,379Front axle tractor tandem 75,175 149,015Back axle tractor tandem 73,840
Front axle trailer tandem 69,392 151,240Back axle trailer tandem 81,847
lives for the life-cycle analysis needs to be predicted. The MEPDG programme, version 1.1
(Applied Research Associates, Inc., 2009), was used to predict the service lives because it is
partially based on mechanistic theory.
5.1. MEPDG input
5.1.1. Traffic
The traffic applied on Cells 77, 78, and 79 is an 18-wheel, 5-axle tractor/trailer with the loading
configurations of gross vehicle weight of 355.9 kN (80 kips), as shown in Figure 6 and Table 3
(Minnesota Department of Transportation, 2009). The truck runs on these three cells during a
normal 8-hour working time with an average of 48 laps per day. The real traffic information was
input into the MEPDG software to predict future performance.
5.1.2. Climate
The Cells 77, 78, and 79 are located about 64 km (40 miles) north-east of Minneapolis, MN.The hourly climatic data of the nearest station were exported from the climatic database provided
in the MEPDG programme
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 8/15
544 X. Li et al.
Table 4. Summary of service life analysis.
Time to failure (month)
Distress Cell 77 (RPM) Cell 78 (Class 6) Cell 79 (RPM + CHCFA)
AC surface down cracking 132 90 >300AC bottom-up cracking >300 >300 >300AC thermal fracture 144 144 144Total rutting >300 >300 >300IRI 270 270 282Service life (Year) 11 7.5 23.5Rehabilitation times (within
service life of Cell 79)1.14 2.13 0
5.2. Predicted performance
The performance of Cells 77, 78, and 79 were predicted by MEPDG software with same traf-fic, climate, HMA surface layer, and subgrade properties. Only the properties of the base-layer
materials were different as shown in Figure 4. A reliability of 90% was used in the modelling.
The performance modelling results are summarised in Table 4. It can be seen that the time to
thermal cracking failure is same for Cells 77, 78, and 79, which is 144 months. This is because the
same HMA material was used in the three cells. However, the purpose of this study is to compare
the performance of base materials. Therefore, the modelling results of other distresses such as
top-down cracking, bottom-up cracking, rutting, and IRI which are related to the materials of base
course were used to determine the service lives.
6. Life-cycle cost analysis and results
Life-cycle cost analysis (LCCA) is an effective way to assess the cost of the construction operation
over the service life (Mearig, Coffee, & Morgan, 1999). The RealCost software of version 2.1
which was developed by Federal Highway Administration (2004) was used to perform the cost
analysis.
Based on the MEPDG performance prediction, the service life of Cell 79 with CHCFA-
stabilised RPM is 23.5 years, which is about twice the service life of Cell 77 with RPM base
(11 years, Table 4), and about three times the service life of Cell 78 with Class 6 aggregate base
(7.5 years, Table 4). The typical rehabilitation of surface milling and HMA overlay was assumed
at the end of each service life. It is assumed that the overlay life is essentially same as that of the original asphalt pavement life (Wisconsin Department of Transportation, 2011). Therefore,
for Cell 77, the rehabilitation would be carried out at 11 and 22 years. At the end of 23.5 years,
the pavement would be still there and had a remaining service life of 9.5 years. For Cell 78,
the rehabilitation would be carried out at 7.5, 15, and 22.5 years. At the end of 23.5 years, the
pavement would be still there and had a remaining service life of 6.5 years. The salvage value
was considered in the LCCA. No maintenance cost was considered in this study. A 3% inflation
rate was assumed in the analysis.
For the convenience of comparison, the procedure of the rehabilitationwas assumed to consist of
milling of the entire roadway surface, the application of tack coat to the milled surface, placement
of HMA overlay, and the compaction of the HMA overlay. The depth of the milling and thethickness of the HMA overlay were assumed to be 7.62 cm (3 in.) (Washington State Department
of Transportation 2005) for both Cell 77 with untreated RPM base course and Cell 78 with Class
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 9/15
Road Materials and Pavement Design 545
$0
$10,000
$20,000
$30,000
$40,000
$50,000
$60,000
$70,000
$80,000
$90,000
Cell 77 (RPM) Cell 78 (Class 6) Cell 79(RPM+FA)
N P V
o f L i f e C y
c l e C o s t s ( $ )
Base Materials of Cells
Life Cycle Cost ($)
HMA Overlay
Milling
HMA Surface
Re-work Due toWeather
OriginalConstruction
$0
$20,000
$40,000
$60,000
$80,000
$1,00,000
N P V
C o s t ( $ )
Items
Life Cycle Cost ($)
Cell 77 (RPM)
Cell 78 (Class 6)
Cell 79
(RPM+CHCFA)
Figure 7. Comparison of life-cycle costs.
6 aggregate base course. There will be no rehabilitation within the 23.5 years of life-cycle analysis
period for Cell 79 with the CHCFA-stabilised RPM base. The cost analysis results were reported
as net present value.
The comparison of the life-cycle costs are shown in Figure 7 which indicates that, from the
life-cycle point of view, Cell 79 with the CHCFA-stabilised RPM base has the lowest cost and
Cell 78 with the Class 6 aggregate base has the highest cost. The ratio of the life-cycle cost of
Cells 77, 78, and 79 is 1.57:2.34:1. Even when the cost of the reconstruction of the base due to
the rain was not considered, the ranking of Cells 77, 78, and 79 remains the same.
7. Life-cycle energy and greenhouse gas analysis and results
The method of determining the life-cycle energy consumption and greenhouse gas emission is
relatively straightforward. First, the construction material quantities were determined for original
construction and projected rehabilitation. Second, the energy consumption and the greenhouse
gas emission per unit construction material was determined as reported by others (Halstead, 1981;
Meil, 2006). Finally, the energy consumption and the greenhouse gas emission were obtained by
multiplying the unit value by the quantities of construction materials.The assumption of the rehabilitation procedure was the same as that in the LCCA. The same
procedure as calculating the salvage value in the LCCA was used in the energy and greenhouse gas
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 10/15
546 X. Li et al.
Table 5. Energy consumption and greenhouse gas emission of Cells 77, 78, and 79.
Total CO2 TotalItems Energy (MJ) energy (MJ) (Mg) = GWP CO2 (kg)
RPM (Cell 77) 1,273,149
(with ForceAccount)1,195,537(withoutForceAccount)
27,144 (with
ForceAccount)27,139(withoutForceAccount)
Initial constructionBase
Materials production 24,425 2.84
Materials transportation 0 0.00
Processes (equipment) 3313 0.25
Force Account (due to rain) 77,612 5.00
HMA surface 623,547 14,149.87
Rehabilitation
Milling (twice-salvage) 12,821 1059.10
HMA overlay (twice-salvage) 531,432 11,926.71
Class 6 Agg. (Cell 78) 1,823,287(with ForceAccount)1,745,675(withoutForceAccount)
38,542 (withForceAccount)38,537(withoutForceAccount)
Initial construction
Base
Materials production 81,803 7.14
Materials transportation 13,147 0.98
Processes (equipment) 5435 0.41
Force Account (due to rain) 77,612 5.00
HMA surface 623,547 14,149.87
Rehabilitation
Milling (thrice-salvage) 24,069 1988.28
HMA overlay (thrice-salvage) 997,674 22,390.41
RPM + FA (Cell 79) 661,728 (withand withoutForceAccount)
14,154 (with and without ForceAccount)
Initial construction
Base
Materials production 24,425 2.84
Materials transportation 9141 0.68
Processes (equipment) 4615 0.35
Force Account (due to rain) 0 0.00
HMA surface 623,547 14,149.87
Rehabilitation
No 0 0.00
analysis. PaLate programme was used to determine life cycle energy consumption and greenhouse
gas emission (Horvath, Pacca, Masanet, & Canapa, 2003).
7.1. Energy analysis
The energy involved in highway development consists of construction energy, transport energy,
processing energy, and calorific energy (Halstead, 1981). The calculation results of the life-cycle
energy consumption are shown in Table 5. As indicated in the introduction of construction,
for Cells 77 and 78, the subgrade and base course were reconstructed due to the rain water.The energy consumed during the reconstruction due to precipitation is indicated as ‘Force
Account’ in Table 5 The ratio of the life cycle energy consumption between Cells 77 78 and
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 11/15
Road Materials and Pavement Design 547
Figure 8. Comparison of life-cycle energy consumption (considering reconstruction due to rain).
79 are 1.92:2.76:1 and 1.81:2.64:1, respectively, with and without considering the reconstruction
due to rain. Figure 8 shows the comparison of the life-cycle energy consumption of Cells 77,
78, and 79, considering the reconstruction due to rain. Cell 79, with the CHCFA-stabilised RPM
base, has lower life-cycle energy consumption than Cell 77 with RPM base, followed by Cell 78
with Class 6 base. This conclusion would remain the same if the reconstruction due to rain was
not considered.
7.2. Greenhouse gas emissions analysis
The greenhouse gasses CO2, CH4, N2O, etc. were converted to a measure of direct global warm-ing potential (GWP) using the well-accepted CO2 equivalence method as developed by the
International Panel on Climate Change The calculation results are shown in Table 5 Because
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 12/15
548 X. Li et al.
Figure 9. Comparison of life-cycle greenhouse gas emission (considering reconstruction due to rain).
the CO2 emission during the subgrade and base reconstruction is very small, the ratio of the life-cycle CO2 emission between Cells 77, 78, and 79 is the same as 1.92:2.72:1, with and without
considering the reconstruction. The life-cycle CO2 emission is plotted on a log scale in Figure 9.
It can be seen that Cell 79 has the lowest CO2 emission, followed by Cells 77 and 78.
8. Conclusions and recommendations
This paper studied the use of CHCFA-stabilised RPM as a base material and compared it to
unbound RPM and crushed aggregates, in terms of pavement lives and life-cycle analysis of costs,
energy consumption, and greenhouse gas emission. The conclusions can be drawn as follows:
(1) The back-calculated moduli of the base courses from FWD tests were extremely higher
during the Winter seasons when the base course materials were frozen The moduli of base
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 13/15
Road Materials and Pavement Design 549
courses were lower in Spring than the moduli in other seasons, indicating the weakening
of materials by Spring thaw.
(2) The back-calculated moduli of CHCFA-stabilised RPM in the field does not show
significant increase with the increase of curing age.
(3) The CHCFA-stabilised RPM has much higher resilient modulus at 28 days curing age
than that at 7 days of curing age, and has much higher resilient modulus than untreated RPM and Class 6 aggregate.
(4) Based on the MEPDG performance prediction, the service life of Cell 79 with CHCFA-
stabilised RPM is 23.5 years, which is about twice the service life of Cell 77 with RPM
base (11 years), and about three times the service life of Cell 78 with Class 6 aggregate
base (7.5 years).
(5) The life-cycle analysis indicates that the usage of the CHCFA-stabilised RPM as the base
of the flexible pavement can significantly reduce the life-cycle cost, energy consumption,
and greenhouse gas emission compared with the untreated RPM and Class 6 aggregate
base.
Follow-on performance monitoring of Cells 77, 78, and 79 is needed to validate the MEPDG
performance prediction.
Acknowledgements
The authors want to express their appreciation to the US Department of Energy for funding this study and Minnesota Department of Transportation for their cooperation during the construction and field studies and Mathy Technology & Engineering Services, Inc. for performing the binder test. Thanks are given to theAdvanced Transportation Research and Engineering Laboratory at the University of Illinois at Urbana-Champaign for the laboratory testing of the properties of the HMA.
References
Applied Research Associates, Inc. (2009). M-EPDG mechanistic-empirical pavement desigh guide (version1.1). Retrieved from http://onlinepubs.trb.org/onlinepubs/archive/mepdg/software.htm
Bhatty, J. I., Gajda, J., & Miller, F. M. (2003). Commercial demonstration of high-carbon fly ash technologyin cement manufacturing . 2003 International Ash Utilization Symposium, Center for Applied EnergyResearch, University of Kentucky. Paper #38.
Clyne, T. R., & Palek., L. E. (2008). 2007 low volume road & farm loop cells 33, 34, 35, 77, 78, 79, 83, 84construction report . Maplewood: Minnesota Department of Transportation.
Federal Highway Administration. (2004). RealCost V. 2.1. Program developed by Federal HighwayAdministration, Washington, DC.
George, K. P., Bajracharya, M., & Stubstad, R. (2004). Subgrade characterization employing the fallingweight deflectometer. Transportation Research Record: Journal of the Transportation Research Board ,1869, 73–79.
Halstead, W. J. (1981). Energy involved in construction materials and procedures. Washington, DC: NationalResearch Council, Transportation Research Board.
Horvath, A., Pacca, S., Masanet, E., & Canapa, R. (2003). PaLATE program. Berkeley: University of California.
Koch, S., & Ksaibati, K. (2010). Performance of recycled asphalt pavement in gravel roads. Laramie:University of Wyoming.
Li, L., Benson, C. H., Edil, T. B., Hatipoglu, B., & Tastan, O. (2008). Evaluation of recycled asphalt pavement material stabilized with fly ash. ASCE Geotechnical Special Publication, GSP 169, Geo-Denver, Denver,CO.
Mearig, T., Coffee, N., & Morgan, M. (1999). Life cycle cost analysis handbook . Juneau: State of Alaska – Department of Education & Early Development.
Meil, J. (2006). A life cycle perspective on concrete and asphalt roadways: Embodied primary energy and global warming potential (Research Report to Cement Association of Canada)
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 14/15
550 X. Li et al.
Minnesota Department of Transportation. (2009). MnROAD semi tractor trailer . St. Paul, MN: Author.Ramme, B., & Tharaniyil, M. (2000). Coal combustion byproduct utilization handbook . Milwaukee, WI:
We Energies.Senior, S. A., Szoke, S. I., & Rogers, C. A. (1994). Ontario’s experience with reclaimed materials for use
in aggregates. Presented at the International Road Federation Conference, Calgary, Alberta.Sullivan, J. (1996). Pavement recycling: Executive summary and final report (Report No. FHWA-SA-95-
060). Washington, DC: Federal Highway Administration.Texas Transportation Institute. (2001). MODULUS 5.0 for DOS . Program developed by Texas Transportation
Institute, College Station, TX.Washington State Department of Transportation. (2005). WSDOT pavement policy, p. 17. Olympia, WA:
Author.Wisconsin Department of Transportation. (2011). Facilities development manual: Pavement . Madison.
Retrieved March 27, 2011, from http://roadwaystandards.dot.wi.gov/standards/fdm/14-00toc.pdf Witczak, M. W. (1997). Harmonized test methods for laboratory determination of resilient modulus for flexi-
ble pavement design (National Council Highway Research Program Report 1-28A Report). Washington,DC: Transportation Research Board of National Academies.
Witczak, M. W. (2004). Laboratory determination of resilient modulus for flexible pavement design (NationalCooperative Highway Research Program (NCHRP) 1-28A, Research Results Digest, No. 285, January).
Washington, DC.
7/24/2019 Cost Energy Ash in Place Stabilized
http://slidepdf.com/reader/full/cost-energy-ash-in-place-stabilized 15/15
Reproduced with permission of the copyright owner. Further reproduction prohibited without
permission.